For example, a hard disk drive as a storage device is used as a storage device for a personal computer or a hard disk drive (HDD) recorder. The storage (or recoding) density of the hard disk is currently increasing year after year.
Thus, in recent years, a vertical (or perpendicular) magnetic recording technique is adopted in place of a longitudinal recording technique, thereby further increasing the storage density.
Also, to further increase the storage density, research and development of various media, such as BPM, have been actively conducted.
FIG. 17 is a schematic drawing for briefly explaining a track structure inside of a general BPM.
A BPM 100 depicted in FIG. 17 has a plurality of magnetic dots 101 disposed in a magnetically separated manner each with a predetermined space in a down-track direction (bit-length direction) to allow data to be written or allow written data to be reproduced with application of a magnetic field, and also has a plurality of tracks 102 disposed in a magnetically separated manner in a cross-track direction orthogonal to the down-track direction.
The BPM 100 has a configuration in which the magnetic dots 101 are disposed in a magnetically separated manner each with the predetermined space in the down-track direction and the cross-track direction. Therefore, as for the down-track direction, side erase to an adjacent track 102 can be prevented. As for the cross-track direction, the bit density is increased, thereby significantly increasing the storage density.
Also, in the conventional HDD device, in place of using BPM, a technology is known as a method of resolving a phase shift (or phase error) in write timing, in which a write-once magnetic storage medium is implemented and a clock-correcting successive pattern is additionally written for clock correction (for example, see Japanese Laid-open Patent Publication No. 08-36839).
However, in the magnetic storage media, such as BPM, the magnetic dots 101 for writing or reproducing data are disposed in a magnetically separated manner in the down track direction and the cross-track direction and taken as a fixed pattern. Therefore, if a phase shift occurs in write timing with respect to the magnetic dots 101, different data may be written in the magnetic dots 101 adjacent in the down-track direction.